In the course of manufacturing of a web material such as a sheet plastic, paper, or the like, the material passes between one or more rolls which compress the material into the desired shape. In the course of manufacturing such web material, it is important to maintain the temperature of such rolls within narrow tolerances. The manufacture of some materials require the application of heat to the material from the roll, whereas other processes require that the roll cool, or chill the material. If the temperature of the roll is not properly monitored, the material being manufactured will not have the desired consistency and may, for example, stick to the roll and cause irregularities in the webbed product manufactured.
In order to maintain a roll at a desired temperature, such heat transfer rolls provide for a heating or a cooling liquid to be injected through a bore in the shaft at one end of the roll. The liquid is then directed through a plurality of spiralled channels positioned within the roll and adjacent the outer cylindrical surface thereof. After passing through the spiral channels across the length of the roll, the liquid is emitted through a second bore in the shaft at the opposite end of the roll.
The liquid, which is recycled through the channels of the roll, gradually deposits impurities in the channels of the roll, which is generally referred to as scaling. Over a period of time, the scaling within the channels of the roll will inhibit the flow of liquid therethrough and eventually it will not be possible to maintain the roll at the desired temperature, causing defects in the product manufactured. The scaling may occur evenly throughout the channels of the roll, or scaling may become concentrated in one or more channels and may ultimately result in altogether blocking one or more channels. When an operator cannot maintain the roll at the required temperature, the roll must be serviced, and the scaling within the channels removed.
Currently, such rolls can be descaled by injecting a cleaning chemical through the bore in the shaft at one end, through the channels, and out the bore in the opposing end. As the cleaning solution dissolves the accumulated material within the channels of the roll, the chemical makeup of the cleaning solution become altered, and to monitor the descaling certain chemical qualities, such as the pH of the discharged cleaning solution, are recorded. When it is apparent that the cleaning solution is no longer dissolving deposits, the channels are presumed to have been cleaned and the roll can be placed back in service.
Although rolls may generally be descaled as described above, the process consumes a considerable amount of time and chemicals. When, for example, scaling is concentrated in one or more channels, the cleaning solution will tend to freely and quickly flow through the open channels but move slowly through the congested channels, such that the cleaning of a congested channel may consume an inordinate amount of time and chemical. Furthermore, if one or more channels is completely clogged, the cleaning solution may fail to descale the channel altogether. In such cases, a service technician monitoring the discharge of cleaning solution may conclude that the channels of the roll have been descaled when, in fact, the problem is unsolved. When the scaling within the single channel of a roll totally blocks the movement of liquid therethrough, it may be necessary to disassemble the roll by removing the outer surface thereof to obtain access to the channels so that they may be manually descaled. This process, however, is extremely expensive and time consuming, and results in the entire rebuilding of the roll.
It would be desirable to provide a method and apparatus whereby a descaling and cleaning solution may be directed through any one of the plurality of channels in such heat transfer rolls such that the channels may be individually descaled.